Scientists have long believed that the adult brain grows new neurons, but a study published in Nature casts doubt on the conventional wisdom. Researchers collected postmortem or intraoperative tissue from the hippocampi of 59 people ranging in age from fetal stages up to 77 years, used a technique involving antibodies to detect the development of neurons, and concluded that neurogenesis declines sharply within the first year of life and halts by adulthood.